Modeling compression behavior of cement-treated zinc-contaminated clayey soils

In this paper, the compression behavior of cement-treated soil with various cement contents and zinc concentrations is presented and modeled by the destructuring framework and the concept of the Intrinsic Compression Line (ICL). The void ratio of a cement-treated sample with Zn contamination is the sum of the void ratio sustained by the intrinsic soil fabric (destructured void ratio) and the additional void ratio due to cementation. The compression index at the pre-yield state, C_s, increases as the Zn concentration increases or as the cement content decreases. At the post-yield state, the additional void ratio is inversely proportional to the effective vertical stress. The rate of reduction in the additional void ratio is controlled by the destructuring index, b. The values for b and yield stress are mainly dependent upon the degree of cementation, which is controlled by the cement content and the Zn concentration. Based on a critical analysis of the test data, a practical (simple and rational) method for assessing the compressibility of cement-treated soil with various Zn concentrations is suggested. The proposed predictive method is useful not only for quickly determining compression curves, with acceptable errors, but also for examining the results of tests on cement-treated zinc-contaminated soil.     

深层水泥土桩在软土地基加固中的应用

结合工程实例 ,对深层搅拌水泥土桩加固软土地基的设计与施工作一介绍 ,根据工程地质条件和基础设计要求 ,分析并确定了地基加固处理方案 ,且对复合地基的相关因素进行了探讨 ,提出了该工程采用深层搅拌水泥土桩的桩径、桩长、桩数 ,以及施工参数和工艺要求 ,对加固处理效果进行了总结     

浆喷桩在基坑开挖中的支护与防渗作用

泉州市石狮伍堡污水处理厂由于临近晋江入海口，地基以砂质土和淤泥质土为主，地下水丰富且受潮汐 影响较大。在污水积水池深达５．０ｍ的基坑开挖中，对基坑坑壁的支护与防渗要求较高，文中介绍浆喷搅拌桩对此问 题的解决，并论述其效果。     

Evaluation of statistical uncertainty of cement-treated soil strength using Bayesian approach

The statistical parameters for the strength of cement-treated soil are evaluated by the strength of cored samples retrieved from cement-treated columns for a quality assurance procedure in the deep mixing method. The sample parameters include the statistical uncertainty associated with the statistical sample size and other factors. Therefore, a probabilistic characterization of the statistical parameters of strength is required to quantify the statistical uncertainty in the quality assurance process. This paper presents a quantitative analysis of the statistical uncertainty for the estimation of the strength of cement-treated columns. The Bayesian approach is adopted to evaluate the statistical uncertainty occurring in the determination of the statistical parameters of the strength from observed data. The inference is performed via a Markov chain Monte Carlo method, in which samples of the parameters are sequentially drawn from a joint posterior probability distribution. An example analysis is performed to illustrate the statistical uncertainty of the unconfined compressive strength of cored samples retrieved from cement-treated columns. The results show that the statistical parameters, inferred from the data with the sample size of approximately 40, include considerable uncertainty. The variability of the estimated statistical parameters is found to depend on both the sample size and the spatial correlation. The influence of the statistical uncertainty, caused in the estimation of the mean and standard deviations in strength, is examined within the framework of quality assurance in the deep mixing method.     

复合地基中桩土应力数值分析

采用有限元分析方法和Duncan Chang土体本构模型对深层搅拌桩复合地基的桩体荷载传递规律、桩土应力比分布特性及影响因素进行了系统分析 ,得出了有益的结论。     

Forecast formula for strength of cement-treated clay

A simple formula with no fitting parameters is proposed, with which the strength of cement-treated soil can be calculated at any curing time with the known cement-water ratio (the ratio of the cement mass to the mass sum of the water in the soil and the water in the cement paste) of the cement-treated soil and the corresponding strength at a certain short curing time. The results obtained with this formula basically reflect the law whereby the strength of cement-treated soil increases with the curing time. To further facilitate the use of this formula, the conversion relation of the cement-water ratio to the cement-mixed ratio and the water-cement ratio of the cement paste were presented. In such a way, the strength of cement-treated soil can be predicted directly using the common proportioning parameter of the cement-treated soil. In addition, with the known long-term (within 180 d) target strength of the cement-treated soil, its short-term strength can also be speculated through this formula, on whose basis a formulation design for cement-treated soil may be conducted as well.     

Performances of SDCM and DCM walls under deep excavation in soft clay: Field tests and 3D simulations

This study presents the results of full-scale tests and three-dimensional finite element analyses of deep cement mixing (DCM) and stiffened deep cement mixing (SDCM) columns under lateral loads and DCM and SDCM walls under deep excavation in soft clay. The DCM walls used in this study comprised one, two and three rows of DCM columns, whereas the SDCM walls consisted of only one row of DCM columns with steel H-beams inserted in either all DCM columns or in alternating DCM columns. The measured and simulated results are presented in terms of profiles of lateral displacement, settlement and bending moment.     

关于土的前期固结压力试验中几个问题的探讨

介绍了一种比较简捷而准确地在e—logp曲线上求取最小曲率半径Rmin点O,以求取土的前期固结压力pc值的方法,并提出影响试验成果的几个重要因素,以指导实践中准确判断土层的压密状态。     

深厚软土场地基坑支护设计和施工的几点体会

本文介绍在深厚软土场地的深层搅拌桩重力式挡土墙设计中,采用改变挡土墙截面形状,桩位布置和适当放坡等方法以适应不同软土地层分布和周边条件。     

粉土液化特性的试验研究

利用TYD-20动三轴实验机对杭州湾附近的近海粉土，模拟不同的波浪荷载作用下相同固结比的不排水动三轴的动强度和液化试验，对所得的试验结果进行比较，研究频率改变对液化特性的影响，从而总结不同的振动频率和不同的振幅对粉土液化强度的影响程度，为判断粉土液化的可能性和附加变形提供科学有效的分析方法。     

深层搅拌法在清水池软弱地基加固中的应用

某实际工程采用深层搅拌法处理清水池的软弱地基 ,取得了良好的效果 ,可供相近工程参考。     

水泥土及加劲水泥土搅拌桩施工技术发展现状

综述了水泥土搅拌桩及加劲水泥土搅拌桩在国内外的技术发展现状 ,着重阐述了近年在我国的各种应用 ,以及固化剂的配合比与水灰比 ,H型钢起拔机 ,桩的竖向抗压承载力等。     

连续式振动搅拌原理的试验

本提出的连续式振动拌和方案经试验得到了验证和改进，对拌和稳定土有良好的效果，对拌和水泥混凝土需进一步完善。     

水泥与水泥磷石膏粉喷桩静载试验

采用水泥与水泥磷石膏固化剂的粉喷桩复合地基工程的静载试验对比，说明在水泥中掺入适量的磷石膏的方法，在深层搅拌法加固软土地基的工程中有推广价值。     

超长水泥土搅拌桩的荷载传递特性

大型构筑物实体下超长水泥土搅拌桩的桩身应力和变形观测结果表明,对桩身质量良好的水泥土桩,在长期荷载作用下呈现出接近刚性摩擦桩的荷载传递特性和较高的桩土应力比,并且,只要桩身中下部水泥土强度有保证,群桩中桩身轴力的有效传递深度可达25m以上.     

水泥土搅拌桩止水帷幕工程特性研究

水泥土搅拌桩作为基坑止水帷幕已经得到了广泛应用,为了更深入的理解作为止水帷幕的水泥土的工程特性,通过对不同水泥掺入量的水泥土无侧限抗压强度和渗透系数的室内试验研究,利用CBR-1承载比试验仪和TSS-2柔性壁三轴渗透仪对水泥土进行了无侧限抗压强度和渗透试验,分析了养护龄期及水泥掺入量对水泥土的无侧限抗压强度和渗透系数的影响。试验结果表明,水泥土的无侧限抗压强度随养护龄期和水泥掺入量的增大而增大,并通过曲线的拟合,得出了无侧限抗压强度的预测公式;渗透系数随养护龄期和水泥掺入量的增大而减少,通过数据对比得出28天之后水泥土渗透系数主要是受水泥掺入量的影响。     

水泥土桩复合地基的发展现状与应用研究

本文介绍了水泥土桩复合地基的相关研究进展,其中包括材料性能对水泥土桩复合地基的影响、水泥土桩复合地基承载和变形的试验研究、水泥土桩计算模型及受力分析、变形分析。旨在为今后水泥土桩工作机制及破坏形式的深入研究提供理论基础。     

深层搅拌桩接杆法施工在工程中的应用

本文结合工程实例介绍深层搅拌桩的接杆法施工工艺和施工要点。阐述深层搅拌桩在施工净高受限制时,采用接杆法施工工艺,可取得了较好的技术经济效果。     

深层搅拌桩复合地基沉降变形研究

通过现场复合地基静载荷试验和桩土应力比的测试,探讨了水泥土复合地基桩距拉大以后桩土应力比和承载变形机理。对桩距s=(2.57~2.64)d的复合地基而言,由于搅拌桩周侧摩阻力的充分发挥,桩间土中的应力不会相互叠加,使复合地基的加固区形成较为坚实的“加筋复合垫层”,从而有效扩散应力,使得复合地基的沉降量大大减小。